Digital Vernier Caliper 0-150mm

A bike comes in with a stubborn headset that the customer keeps tightening. The cup-and-cone adjustment is in spec, the fork crown clears the head tube cleanly, the bearings feel good. Five tries later, nothing's changed. The thing you haven't checked is whether the head tube itself has gone slightly oval. The 270A Digital Vernier Caliper is what tells you that in three seconds; by measuring the head tube ID at two perpendicular axes and reading the difference on the screen.

The 270A reads 0–150 mm (0–6 in) with official accuracy of 0.02 mm / 0.001 in to DIN 862. Resolution on the LCD is 0.01 mm / 0.0005 in; the in/mm button switches the dual scale. The finish is trivalent chrome plated and the beam is marked STAINLESS HARDENED. Official functions are internal, external, depth, and step measurement.

What it measures, in practical bike-shop terms

• Rotor thickness against the manufacturer's published minimum (Shimano typically 1.5 mm minimum on common road rotors)
• Axle outer diameter when sourcing a matching dust seal or bearing
• Head-tube ID across two perpendicular axes (the oval-detection check)
• Steerer outer diameter at a sleeved section vs. an unsleeved section
• Cassette spacer thickness when verifying a 142x12 vs. 148x12 conversion
• Spoke length (with the depth jaw extended) when verifying a wheel build's spoke order

The 270A is a precision instrument. That means it gets damaged by being dropped on a concrete floor, by being soaked in parts cleaner, or by being run through the bench grinder by mistake (yes, this has happened). Keep liquid out of the slider and do not drop it; the official 270A manual calls out both as electronics-killing mistakes.

Specs

• 0–150 mm / 0–6" range
• Resolution 0.01 mm / 0.0005 in; official accuracy 0.02 mm / 0.001 in (DIN 862)
• Trivalent chrome plated; beam marked STAINLESS HARDENED
• Internal, external, depth, and step measurement
• OFF/ON, in/mm, and ZERO; dual mm and inch scale
• Power: one CR2025 3.0 V lithium cell (official average life: 1 year continuous, 3 years normal use)
• 1-year warranty
• Article 270A · SKU 619881 · length 235 mm · jaw height 40 mm · 460 g

Built in Zreče, Slovenia

Unior has been forging hand tools in Zreče since 1919, and sponsors professional road and mountain-bike race teams. The 270A is the digital companion to our analog Vernier Caliper 271. The 271 analog sibling publishes the same 0.02 mm / 0.001 in accuracy and DIN 862 standard on a battery-free vernier scale; the 270A is the digital member of that pair (460 g, official 1-year warranty, CR2025).

Pro tip from our mechanics

The single best diagnostic for a customer's stubborn headset adjustment is verifying the head tube hasn't ovalized. A 0.05 mm difference across the head tube ID is enough to drive a customer crazy with a headset that won't stay adjusted. Two seconds with the 270A and you have the answer. Our workshop hand tools guide covers the measurement layer of the shop in detail: Workshop hand tools every bike shop needs →

FAQ

What range, resolution, and accuracy does the 270A digital caliper have? Official range is 0–150 mm and 0–6 in on a dual millimeter-and-inch scale. The product page publishes accuracy of 0.02 mm / 0.001 in to DIN 862. The official 270A instruction manual lists resolution of 0.01 mm / 0.0005 in, and banded accuracy of ±0.02 mm from 0–100 mm and ±0.03 mm from 100–200 mm (this article stops at 150 mm).

What can the 270A measure on a bike? Official functions are internal dimensions, external dimensions, depth, and steps. That covers rotor thickness, axle and steerer OD, head-tube ID, spacer stacks, and spoke length with the depth rod. Buttons are OFF/ON, in/mm, and ZERO.

How is the digital 270A different from the analog 271? Both publish the same 0.02 mm / 0.001 in accuracy, DIN 862, 0–150 mm / 0–6 in range, and the same four measuring functions. The 270A is digital (LCD resolution 0.01 mm, one CR2025 battery, 460 g, official 1-year warranty). The 271 is the analog, battery-free sibling (240 g, no warranty badge). They are separate instruments, not a spare for each other.

What battery, size, and finish does the 270A use? One CR2025 3.0 V lithium cell (official average life: 1 year continuous, 3 years normal use). Length 235 mm, jaw height (B) 40 mm, 460 g. Finish is trivalent chrome plated. The beam on the official product photo is marked STAINLESS HARDENED. Article 270A, SKU 619881.